1. Field of the Invention
The present invention relates to a hybrid drive device including as driving sources an engine (for example, an internal combustion engine such as a gasoline engine and a diesel engine) and a rotating electrical machine (including, for example, a rotating electrical machine serving as a motor for receiving electric power supply and generating driving force (for example, rotational driving force), a rotating electrical machine serving as a generator for receiving driving force and generating electric power, or a rotating electrical machine serving either as a motor or a generator depending on the operation state) and structured to obtain driving force from one or both of the engine and the rotating electrical machine, perform shifting in a transmission, and transmit the resultant driving force to driving wheels so that a vehicle travels.
2. Description of the Related Art
The applicants introduced a hybrid drive device described in Japanese Patent Application Publication No. JP-A-2004-001708 as an example of a hybrid drive device. An object of the technology disclosed in JP-A-2004-001708 is to provide a hybrid vehicle drive device having a structure with reduced a dimension in an axial direction as compared to a related device without increasing a dimension in a radial direction, while using an engine and a motor, which are connected together as a power source.
The hybrid vehicle drive device described in Japanese Patent Application Publication No. JP-A-2004-001708 includes an annular motor centering around the axis of an engine output shaft, a starting device for transmitting driving force from the engine and motor to a transmission downstream side, and a transmission for receiving the driving force of the engine and motor through the starting device. In this drive device, the starting device includes a starting clutch and a damper device, which have an annular shape centered around the aforementioned axis and are arranged spaced apart from each other at a predetermined distance in an axial direction. The starting clutch is provided so that at least a part of the starting clutch overlaps the motor in an axial direction, and the starting clutch is located on an inner-diameter side of the damper device.
As shown in JP-A-2004-001708, this technology uses a structure in which a rotor of a rotating electrical machine is fixed to an outer-diameter part of a clutch hub and rotation of the rotating electrical machine is transmitted directly to an intermediate shaft. When the clutch is in an engaged state, the engine output is also transmitted through the clutch to the clutch hub of the clutch and transmitted to the intermediate shaft.
A hybrid drive device including two kinds of drive sources (an engine and a single rotating electrical machine) and a transmission has originally been developed in order that the occupied space required to mount the hybrid drive device can be reduced as much as possible. As in the related art described above, however, in the case of using the structure in which the output of the driving source (especially the rotating electrical machine) is directly applied to the transmission and transmitted to driving wheels after shifting in the transmission, the size of the rotating electrical machine itself tends to be increased depending on the driving torque required for traveling, which may be against the object of reducing the size of the device.
Moreover, in the case of using the structure in which rotation from both the engine and the rotating electrical machine is reduced in speed in the transmission, the size of the transmission needs to be increased, providing room for improvement.
In order to increase the torque that is generated in the rotating electrical machine, it is mainly necessary to increase the axial length of the stator and rotor of the rotating electrical machine or increase the diameter of the rotating electrical machine so that the torque that can be generated is increased. However, in a hybrid drive device of the present application that is preferably used in, for example, an FF (front engine-front wheel drive) type, the space that can be occupied by the hybrid drive device is limited, and it is therefore difficult to take measures to increase the torque by significantly increasing the diameter of the rotating electrical machine. Moreover, in the case where the axial length of the rotating electrical machine is increased, the axial length of the hybrid drive device (the length in the left-right direction in FIG. 1) becomes too long, which is not preferable.